Ignition apparatus



July 27, 1937. E. B. NowoslELsKl 2,088,384

IGNITION APPARATUS Fiied April 17, 1935 wwwa u wfomvw a" ./.Iwr

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L w 6 w 8 knk n Patented July 27,1937

UNITED STATES PATENT FFICE IGNITION APPARATUS Application April 17, 1935, serial No. 16,882

11 Claims.

This invention relates to spark-plugs, and more especially to spark-plugs for aviation engines. The severe service conditions which are imposed on spark-plugs for airplane motors are familiar to those skilled in the art, as is also the importance of enclosing all parts of the high-tension current-carrying system by a continuous metallic shield to prevent interference with the reception of signals by adjacent radio receiving sets, and

also to protect the exposed parts of the ignition system from detriment by the elements or otherwise.

The object of this invention is to provide a spark-plug, and more especially a shielded sparkplug, the construction of which is such as to prolong its life and toinsure its effectiveness in such service, and to afford convenience, and which is economical to manufacture.

The invention comprises novel features of great utility in spark-plugs, and novel combinations of elements making an improved spark-plug and an improved assemblage of the spark-plug and its high-tension conductor.

Some of the objects are to provide improved electrodes including novel methods of constructing and assembling the electrodes, and of adjusting the spark gap; to provide improved heat cleecting and cooling means; and to provide improvements in the manner of insulating the current; including a novel method of insuring against development of pipes along the edges of the rolled mica sheets employed as part of the insulating means.

Further objects are to provide a shielded sparkplug of compact construction; to make it easy to remove and insert the conductor, and to establish the electrical connections; to guard against injury to insulation parts of the spark-plug and conductor as the result of such operations; to

40 lock the conductor securely against accidental withdrawal; to insure good electrical connection for the high-tension current .to the plug, to the end that the spark-plug may not fail to function; to relieve the conductor shielding of strain and to insure its electrical connection with the body of the spark-plug; vto provide an improved terminal for detachably connecting the insulated high-tension conductor with the plug, in a socket of which the conductor is inserted; to provide a shielded spark-plug having a swiveled connection through which the'conductor is passed and which has a terminal constructed to be fitted into the shield extension of the plug vand to be locked thereto securely yet detachably, the same construction providing a swivel which enables the (Cl. 12S-169) CFI inner elements of the plug as viewed along the' plane indicated at 3-3 in Fig. 2;

Figs. 4 to'8 inclusive, indicate the appearance of the element 86 of Figs. 1 and 2 as it passes through the successive stages in the process of forming it into its final condition.

For the purpose of a shielded aviation sparkplug the metal body I0 of the plug is provided with a shield extension I I which extends upward considerably above the upper end of the spindle I2 to enclose the spindle and the electrical connection between the same and the conductor which leads the high-tension current to the spindle. This shield extension is preferably in one piece with the attaching nut 5, though such unity is not necessary.

Instead of completely closing the space between the shield extension II and spindle I2, I provide a cooling and Ventilating chamber I3 in Athe form of an annular space between the shield ex- `tension II and a long thin cylindrical metallic sleeve I4 having low thermal conductivity, and lined with a tube I5 formed of rolled mica constituting the wall of a second chamber I6 bounded at its lower end by the upper surface of the compressible metal gland I1, and at its upper end by a novel heat deflecting and sealing assembly to be further described. The gland Il; instead o resting directly upon the lower mica stack I8,

as is the usual practice, is in contact with the.

upper end 2l of a sleeve 22 provided for the purpose of absorbing the heat which finds its way into the mica stack I8 and deflecting said heat to the gland I'I and outer wall of the plug. Two other heat deflecting sleeves are shown at 23, and 24, the former resting on the upper surface of the electrode cup 25 secured in position on the base of the spindle I2 by a pressure suilicient to change the cross-section of the upper end of the cup (initially of uniform bore) and cause its contour to conform to that of the spindle base. The part 24- is in the nature of a continuous jacket enclosing the spindle I2 and its insert 21 of some metal (such as copper or silver) having higher conductivity'than the materialsteel, preferablyused in the spindle proper. This sleeve or jacket 24 is shown as closed at its lower end but this closure occurs only after Vthe jacket has been positioned upon the spindle, the jacket being initially, merely a thin tube open at either end. After being placed around the spindle the extending portion of the lower end is bent inwardly to lie iiat against the botto'm surface of the spindle I2 and its insert 21--in other words, to occupy the position indicated in Fig. 2. It will be noticed further that the jacket 24 extends upwardly to a point just above the end of the gland I1 and the point where the centrally bored portion of the spindle begins. Due to the reduction in cross-sectional area at this point, and also by reason of the termination of the jacket 24 at this point, there is a tendency to cut of! much of the upward flow of heatl through the spindle I2 and to deect the heat ilow outwardly and radially into the copper gland I1 from which much of the heat is directly disslpated by the cooling blast circulating adjacent the central shoulder Il of the gland I1, such circulation being produced by reason of the radial openings I2 and the annular chamber 33 communicating therewith. The sleeves 23 and 22 coact with thejacket 24 in diverting heat from the spindle I2 and the electrode 25 to the annular chamber I4 and the copper gland I1, and from said chamber and gland to the atmosphere by way of shell 26 and radial openings 32. In or adjacent the plane of these radial openings 32 there is provided a ,thrust washer 3l through which pressure is applied to the gland I1, and a compressible washerl! is provided to insure a rm bond or seal preventing the escape of the conl'lned cylinder gases, the pressure being applied as a result of threading the shield extension II into the shell Il, the two elements just mentioned being correspondingly threaded as 'indicated at 4I.

As shown clearly in Fig. 2, .the spindle I2 is of reduced diameter at two or more points as indicated at 4I and 44; and the jacket 24, the rolled mica tube 4I, and the sott metal gland I1 are pressed snugly against these peripheral depressions in the spindle as one of the plug assembling operations. This operation of applying pressure laterally results not onLv 'in .a ilrm seal around the spindle I2 but also eliminates any longitudinally extendingv crevices or "pipes" which have heretofore been a source oi' leakage characteristie of rolled mica insulating tubes. '111e wrapping of the mica sheets one around the other tends to leave such crevices running longitudinally oi' the wrapping. but by producing kinks at several points along the length of the wrapping,

as indicated, I have found it possible to eliminate this source of trouble'.

Asameansofmaintainingthemicastack lining Il oftheinner metallic sleeve I4 inposithmandstthesametimeeil'ectingsnadditionalpathforthetransterofheatdirectlyto thesaidsleevellfromwhichitmayberadiated totheatmospherebythecoolingcurrentofair ilvwingalongthechamberllandtheradialapertures2land2,1propetothreadtheupper end lioithespindle I2 andawlytosaid threadedportionllapairofthreadedcollars pered gland I4 of softer material such as copper so that it may, when subjected to the pressure applied -by the tightening of nut 52, form a rm bond with the washer 56 and also with the expansion ring 58 which grips the mica lining I5 at a point approximately midway between its ends, this lining 5l being inserted and expanded in the tube I4 prior to the assembly of said tube within the shield extension II, The associated elements 52, 53, 54 and 56, on the other hand, are iirst assembled separately in position upon the inner plug assembly, and the latter is then dropped in place within the shell 36 prior to bringing the shield extension assemblyinto position. Also prior to attaching the upper assembly there is inserted within the hollowed portion of the spindle, a coil spring 6I and a contact pin 62 having a circumferential shoulder 63 against which the upper end of the spring 6I abuts to urge said pin upwardly into position to contact the radially spread strands of the current conducting wire 68 when' the latter is installed 4in place. Associated with the wire 65 is its covering 61 of insulating material, its outer metallic sheath 68, the swivel connection 69 soldered or otherwise secured thereto, and the attached coupling nut 1I, all oi.' which are brought into assembled relationship with the parts previously described.

As noted above the inner end of the conductor Si extends below the insulating material 61 for a certain distance so that the strands may be spread apart to provide better contact with the end of the pin 62. 'I'he mebthod of fastening the spread apart ends of the c nductor is indicated best in Fig. 3 and includes the provision of a fiat metallic plate 13 having a pair of notches 14 and 15 cut therein on opposite sides of the central aperture y 18 through which the conductor G5 passes. Each of the .spread apart sections of the stranded conductor is inserted into position within each of the slots 14 and 15 and thereupon the plate 1I is pinched at either end to partially close the slots, the slot 15 being shown in the partially 'closed position which it assumes after the pinchand downwardly turned end of a ferrule 1I of low thermal conductivity, the outer portion oi which rests upon the shoulder ll formed near the upper end of the heat dissipating inner wall I4 of the shield extension assembly.

As above indicated, one of the important features of the invention concerns the outer or grounded electrode and method of its manufacture vand installation. The iirst step is to secure an H shaped metallic piece It of suitable heat and spark resisting qualities while at the same time a sumclently good conductor. Such a piece is indicated in Fig. 4. I'his piece is then subjected to abending operation to bring it into substantially the form indicated in Fig. 5. Next the parallel sides I1 and Il are turned into semi-circular arcs which preferably do not quite join (as indicated in Figs. 6 and 7) the crossconnecting portion remaining in the form to which it is initially bent, as shown in Fig. 5. The final step in formation ofthe electrode is to shape the upper annular surface formed by the semi-circular parts l1 and Il so that in transverse section it will have the final appearance indicated in Fig. 2. When thus completed the electrode receives a thin dished washer II of soft metal such as copper and then a second dished Washer 92 of harder material and preferably the same material as the electrode 86 itself. The installation and completion of the electrode assembly is then obtained in the following manner: The shell 36 is placed on a table or workbench with its lower counter-bore 94 uppermost, a thin cup-shaped liner 95 of soft metal, preferably the same material as that of the piece 9|, and centrally apertured to a diameter corresponding to the diameter of the chamber 34, is then inserted in the recessed end 94. The electrode assembly consisting of the parts 86, 9| and 92 is then placed in position within the inverted cup member 95 and the assembly consisting of the parts 36, 95, 92, 9| and 86, is then placed in a ,hydrogen gas furnace or other suitable heat chamber and subjected to a temperature suflicient to cause a fusion or welding along the surfaces of the elements 95 and 9|, with the result that the five elements above enumerated become fused into a permanently welded single unit. This unit is then removed from the furnace, the core assembly, the shield extension assembly, .and upper cable assemblies successively attached thereto inthe respective manners above indicated. When this complete assembly has been accomplished it will be found that the inner electrode 25 occupies a position approaching that of the transverse portion 86 of the outer electrode and also approaching that of the inner cylindrical edge 99 of the thimble 92, forming an auxiliary spark gap, the clearances therebetween being such that the spark will normally jump from the relatively broad surface of the electrode 25 to the correspondingly broad plane surface of the cross-piece 86 of the ground electrode; but if for any reason this normal path of the spark is obstructed-as for example by the formation of ice particles-the spark can then jump from the cylindrical surface of the elec- `trode 25 to the above described cylindrical surface 99 of the thimble 92 which may therefore be considered as a part of the completed electrode. 1n fact, it is, of course, possible tohave the elements 92, 9| and 86 originally formed as an integral whole rather than being composed of three subsequently united pieces as shown.

1t will be noted that the mica tube 46 terminates somewhat above the lower flange of the heat conducting sleeve 23 of copper or other metal, and that therefore a. plurality of the mica disks I8 lie between the end of the mica tube and the said flanged portion of the sleeve. This arrangement has the advantage of facilitating maximum heat transfer from the mica assembly I8 and deflecting such heat to the jacket 24 as well as to the sleeve 22, and at the same time provides a better degree of protection for the lower ends of the layers constituting the completed tube 46. It will also be observed that the cylindrical portion of the sleeve 23 is externally tapered to facilitate a snug grip and seal between parts 46, 23 and 24. In the second embodiment of the invention, as shown in Figs. 8, 9 and 10 there are many elements which are identical in their structure arrangement and functioning to the elements designated by corresponding reference characters in Figs. 1 to 3 inclusive, and these corresponding elements will not be further discussed'in detail. The differentiating'elements are as follows:

For claims to the lunclaimed features disclosed herein, and also disclosed in one or more of my co-pending applications numbered 62,524;

121,216; 121,217; 134,396; and 146,092, filed respectively on February 5, 1936; January 18, 1937;

' January 18, 1937; April 1, 1937; and June 2, 1937,

reference is to be made to said co-pending applications, or to divisions hereof.

What is claimed is:

1. A spark plug comprising the combination of l tween said extension and inner tube, and means d within said tube for directing a flow of heat to said tube lining.

3. A spark plug comprising the combination of .a central spindle, a body having a shield extension thereon, a heat radiating inner tube coaxial therewith, and means for rapidly transferring heat from said spindle to the space between said extension and inner tube.

4. A spark plug comprising the combination of a central spindle, a body having a shield extension thereon, a heat radiating inner tube coaxial therewith, means for rapidly transferring heat from said spindle to the space between said extension and inner tube, said heat transferring means including a metallic ring of high heat conductivity fitting closely against the thinly lined inner surface of said radiating tube, and additional metallic means forniing a continuous heat flow path from said spindle to said metallic ring.

5. A spark plug comprising the combination of a central spindle, a body having a shield extension thereon, a heat radiating inner tube coaxial therewith, a heat conducting metallic jacket surrounding the spindle, and means for rapidly transferring heat from said jacket to the space between said extension and inner tube, said heat transferring means including a metallic ring of high heat conductivity fitting closely against the thinly lined inner surface of said radiating tube,

and metallic wedging means forming a continuous sion thereon, a heat radiating inner tube coaxial therewith, a heat conducting metallic jacket surrounding the spindle and terminating intermediate the spindle ends, thereby leaving a free annular space for heat radiation along the upper length of the spindle, and means for rapidly transferring heat from said free annular space to the space between said extension and inner tube.

'7. A spark plug comprising the combination of a central spindle, a body having a shield extension thereon, a heat radiating inner tube coaxial therewith, a heat conducting metallic jacket surrounding the spindle and terminating intermediate the spindle ends, thereby leaving a free annular spacefor heat radiation along the upper length of the spindle, and means for rapidly transferring heat from said free annular space to the space between said extension and inner tube, said heat transferring means including a metallic ring of high heat conductivity fitting closely against the thinly lined inner surface of forming a continuous heat flow path from said spindle to said metallic ring.

8. A spark plug comprising the combination of a central spindle, a body having a shield extension thereon, a heat radiating inner tube coaxial therewith, a heat conducting metallic jacket surrounding the spindle, and terminating intermediate the spindle ends, thereby leaving a free annular space for heat radiation along the upper length of the spindle, and means for rapidly transferring heat from said free annular space to the space' between said extension and inner tube, said heat transferring means including a metallic ring of high heat conductivity itting closely against the thinly lined inner surface of said radiating tube, and metallic wedging means forming a continuous heat flow path from said spindle to said metallic ring.

9. A spark plug comprising the combination of a central spindle, a body having a shield extension thereon, a heat radiating inner tube coaxial therewith, and means for rapidly transferring heat from said spindle to the space between said extension and vinner tube.

' said radiating tube and additional metallic means 10. A spark plug comprising the combination of a central spindle, a body having a shield extension thereon, a heat radiating inner tube coaxial therewith, and means for rapidly transferring heat from said spindle to the space between said extension and inner tube, said heat transferring means including a metallic ring of high heat conductivity iltting closely against the thinly lined inner surface of said radiating tube, and additional metallic means forming a continuous heat flowv path from said spindle to said metallic ring.

11. A spark plug comprising the combination of a central spindle a body having a shield extension thereon. a heat radiating inner tube coaxial therewith, and means for rapidly transferring heat from said spindle to the space between said extension and inner tube, said heat transferring means including a metallic ring of high heat conductivity tting closely against the thinly lined inner surface of said radiating tube, and

metallic wedging means forming a continuous 

